1. Field of the Invention
The present invention relates to a liquid fuel combustion apparatus in which liquid fuel is vaporized and thus vaporized fuel is burnt and more particularly to improvement of or relating to a liquid fuel combustion apparatus of the type including an ignition plug mounting sleeve which is secured thereto in an improved manner.
2. Description of the Prior Art
To facilitate understanding of the present invention it will be helpful that a typical conventional liquid fuel combustion apparatus is described below with reference to FIGS. 1 to 3. As will be apparent from the drawings, the conventional apparatus essentially comprises a combustion sleeve 12 with a combustion chamber 10 formed therein, an ignition plug 14, an ignition plug mounting sleeve 16 onto which the ignition plug 14 is removably mounted, the ignition plug mounting sleeve 16 being securely fixed to the combustion sleeve 12 and the inner wall thereof being lined with a layer of wick 15 which functions as fuel firing wick, and an annular heat exchanger 18 through which combustion gas generated in the combustion sleeve 12 is caused to flow. In the conventional apparatus combustion air is fed into the combustion sleeve 12 via a combustion air feeding pipe 20, while fuel of which flow rate is controlled and measured by means of a solenoid valve 22 and a fuel pump 24 is introduced into the ignition plug mounting sleeve 16 via a fuel pipe 26. At the same time a part of combustion air flowing through the combustion air feeding pipe 20 is delivered to the ignition plug mounting sleeve 16 via an air pipe 28.
In the conventional liquid fuel combustion apparatus of the above-described type the heat exchanger 18 is generally welded to the combustion sleeve 12 which defines the combustion chamber 10. Likewise, the ignition plug mounting sleeve 16, through which an ignition plug 14 is mounted, is secured to the combustion sleeve 12 by welding, as typically disclosed in Japanese Patent Publication No. 5685/1962. However, since the components constituting the apparatus are connected or secured to one another by welding in the above-described manner, it has been pointed out that the following problems occur with the conventional apparatus as
(1) Welding requires a number of man-hours and leakage tends to occur at the welds. PA0 (2) The elevated temperature developed during welding causes the female thread portion in the ignition plug mounting plug 16 to be undesirably deformed, resulting in difficulty in threading an ignition plug. PA0 (3) The elevated temperature developed during welding causes also undesirable deformation of the combustion sleeve 12. This leads to incorrect orientation of the ignition plug mounting sleeve 16 relative to the direction of flow of combustion air in the combustion sleeve 12. As a result, combustion tends to take place in an incorrect manner. PA0 (4) The inner wall of the ignition plug mounting sleeve 16 is lined with a layer of wick 15 made of asbestos, metallic wire netting or the like each of which functions as firing wick and carbon produced by combustion of liquid fuel tends to be deposited over the layer of wick 15. However, removal of thus deposited carbon is not easily achieved. PA0 (5) During combustion of liquid fuel not only the wick 15 but also the ignition plug mounting sleeve 16 are exposed to the influence of the elevated temperature developed by combustion and therefore they become deteriorated within a shorter period of time than the combustion sleeve 12 and other components. This means that the service life of the whole combustion sleeve is limited by the service life of both the ignition plug mounting sleeve 16 and the wick 15.